docs: def handle_scroll(self, *args):
          """When my ``scroll`` changes, tell my deckbuilder how it's scrolled
          now.
  
          """
          if 'bar' not in self.ids:
              Clock.schedule_once(self.handle_scroll, 0)
              return
          att = 'deck_{}_hint_offsets'.format(
              'x' if self.orientation == 'horizontal' else 'y'
          )
          offs = list(getattr(self.deckbuilder, att))
          if len(offs) <= self.deckidx:
              Clock.schedule_once(self.on_scroll, 0)
              return
          offs[self.deckidx] = self._scroll
          setattr(self.deckbuilder, att, offs)
          self.deckbuilder._trigger_layout()